DURHAM, N.C. – The stringent lockdown imposed by the Chinese government to slow the spread of COVID-19 early this year significantly eased the strain on hospitals there. Admissions due to non-COVID respiratory illnesses decreased by nearly 5,000, a new study by an international team of scientists shows.

“The number of decreased hospitalizations due to air pollution was about the same size or slightly larger than the number of people who went to a hospital for COVID during the same period,” said Drew Shindell, Nicholas Distinguished Professor of Earth Science at Duke University.

The study links the drop in hospitalizations to improved air quality, particularly a nationwide drop in fine particulate matter (PM2.5) pollution, that occurred in the wake of rapid reductions in fossil fuel emissions after the lockdown severely limited transportation and most industrial or commercial activity.

“This is the first study to show that the decreased air pollution during a lockdown can reduce demand for hospital beds and services and keep them from being overrun, which is one of the main short-term goals of flattening the curve,” Shindell said. “What we’ve learned can provide valuable insights for future interventions.”

“These results give us a window into a what a cleaner world could look like—and the paths needed to achieve it,” said Kazuyuki Miyazaki, a scientist in the Tropospheric Composition Group at NASA’s Jet Propulsion Laboratory (JPL) at the California Institute of Technology, who led the study.

The scientists published their peer-reviewed study Oct. 6 in Geophysical Research Letters.

Using satellite measurements, they tracked changes in ozone and PM2.5 air pollution in all Chinese provinces in January and February, starting just before the first lockdown was imposed on hard-hit Hubei province on Jan. 23. The satellite-derived estimates were checked against surface measurements recorded at air-quality monitoring stations during the same time. A model was then used to project how the changing pollutant levels affected the number of hospitalizations, emergency room visits and sick days linked to respiratory or cardiovascular illness during the study period.

The analysis showed that the rapid reductions in nitrogen oxide (NOx) and sulfur dioxide (SO2) emissions that occurred during the lockdown caused PM2.5 pollution to drop by a

whopping 23 micrograms per cubic meter nationwide. This likely resulted in about 60,000 fewer related illnesses – primarily asthma attacks – and 5,000 fewer hospital admissions.

At the same time, however, surface ozone increased by 16 parts per billion over northern China, causing about 2,100 ozone-related ailments and 60 additional hospitalizations there. “Ozone’s response to NOx is well understood to be highly non-linear. In very polluted places like northern China, NOx decreases cause ozone increases,” Shindell explained.

The findings demonstrate that “the COVID-19 lockdown effect on air quality and its human health impacts depends a lot on where and when it occurs,” said Kevin Bowman, engineering and science directorate principal at JPL, who co-authored the study.

“These opposing changes show how complex air quality can be,” said Miyazaki.

Scientists from the Japan Agency for Marine-Earth Science and Technology, the University of Science and Technology of China, and the Royal Netherlands Meteorological Institute co-authored the new study.

Funding came from the NASA Atmospheric Composition Group’s Aura Science Team Program.

CITATION: “Air Quality Response in China Linked to the 2019 Novel Coronavirus (COVID-19) Lockdown,” K. Miyazaki, K. Bowman, T. Sekiya, Z. Jiang, X. Chen, H. Eskes, M. Ru, Y. Zhang and D. Shindell; Oct. 6, 2020. Geophysical Research Letters. DOI: https://doi.org/10.1029/2020GL089252